Sh2-155

Sh2-155 (also known as the Cave Nebula or C 9) is a visible emission nebula in the constellation Cepheus. It is located four degrees SSE of the star ι Cephei, not far from the boundary with the constellation Cassiopeia and M52; It looks like a very faint object, visible with powerful tools or in long exposure photos. The nebula appears as an inhomogeneous collection of bright parts and dark nebulae; the northern part is the least obscured and shows the characteristic reddish colors typical of HII regions. The southern part, on the other hand, is affected by local blackouts; the most notable dark nebula, which gives the complex its name Cave Nebula, is located in the west corner. A short distance from this is a small reflection nebula, known as LNB524, which surrounds a group of ninth-magnitude stars. The distance of the nebula complex is estimated at 2400 light-years from the Solar System.